Posted on: 02 March, 2017

Author: Alexander P

Sex pheromones in the reproductive isolation of lepidopterous species matter. Throughout millions of metamorphoses, evolutionary processes in the Lepidoptera have resulted in many differences in morph... Sex pheromones in the reproductive isolation of lepidopterous species matter. Throughout millions of metamorphoses, evolutionary processes in the Lepidoptera have resulted in many differences in morphology, biology and behavior; not the least subtle of these changes being in the chemical communication systems developed by the various species. Most moth species utilize chemical emanations as a primary stimulus in their specialized mating behavior and the evidence is increasing that in many instances these specialized olfactory cues can also serve as important behavioral barriers to interspecific matings. Although premating mechanisms that operate at close range, such as visual and tactile stimuli, and recognition and stimulatory pheromones (for example, those from abdominal hair pencils), could help effect reproductive isolation, the main premating mechanisms appear to involve circadian and seasonal cycles, habitat preference, geographical distribution and the pheromonal systems. Unique pheromonal systems would be of increased importance in those sympatric species for which the other isolating mechanisms are not very effective with pheromone cologne. Situations for which some type of ecobiotic isolation is required are particularly evident in the lepidopterous family Tortricidae. The phylogenetic relationships evi- dent in the Tortricidae have been discussed quite thoroughly by Powell (1964) and there is also an excellent account of the bionomics of apple-feeding tortricids (Chapman 1973). It is thought that the two major subfamilies, Olethreutinae and Tortricinae, evolved from a single olethreutoid stock, which deposited eggs singly, was a wood borer and had a well-defined annual life cycle. The Tortricinae repre- sent an early divergence from this stock and became external feeders. Some tortrici- nes later developed the habit of depositing eggs in overlapping groups or masses, a habit which resulted in different dispersal activities of the newly hatched larvae and a widening of host plant range for species in the subfamily Tortricinae. The ole- threutines did not evolve along a single line and so some continue to be borers, utilizing the stems, seeds and fruits of their hosts, whereas others are external feeders or semi-internal feeders. The olethreutines do continue the ancestral habit ol‘ laying their eggs singly, and have not developed the wide host range found umong the Tortricinae.  Throughout the evolutionary pheromone processes described above, reproductive separation ol' the various populations was effected by many factors, but we presently find many tortricid species with broadly overlapping mating cycles co-occurring in unlure (Roelofs and Feng 1968; Comeau and Roelofs 1973). Chemical specicity in stimulating premating behavior could, therefore, be particularly important for re- tlucing cross-attractancy. Investigations to date have revealed interesting pheromone structural relationships between and within the two tortricid subfamilies (ta- lulu o.l). The accumulated evidence shows that compounds attractive to o1ethreu- llnc species are usually unsaturated 12-carbon chain acetates, aldehydes or alcohols, whereas attractants for tortricine species are generally found to be 14-carbon chain compounds with unsaturation in the ll-position. Exceptions to this trend are found, however, with Argyrotaenia quadrifasciamz (Fernald) (Tortricinae), which is nllrnctcd to cis-10-dodecenyl acetate, and with the Zeiraphera diniana (Guenée) (( llelhreutinae) attractant, trans-l l-tetradecenyl acetate. Source: Free Articles from ArticlesFactory.com Alexander P is a blogger that studies pheromones. He lives in Los Angeles, CA.